Coin recognition devices, or coin discriminators, are widely used in, e.g., coin counting machines for identifying the type (e.g. denomination) of each coin that is processed by the machine. The known procedures for the recognition of coins analyze in particular the criteria weight, diameter, thickness, electrical-magnetic and light permeable properties of the coin's alloy.
A typical coin recognition device discriminates whether or not coins are acceptable and the denomination of coins by optically detecting method. For example, this coin recognition device includes a light source, a single-chip computer electrically connected to an optical signal receiver, and a display. A passageway is disposed between the light source and the optical signal receiver, for allowing a piece of coin to roll through. A coin backrest is arranged in the passageway. The coin in the passageway transfers along the backrest under drive of a coin propeller. The optical signal receiver extends at least two optical fibers at receiving end thereof. One end of each optical fiber faces toward the passageway and the other end is connected to the single-chip computer by a photoeletric sensor. While one coin rolls through the passageway, parts of the optical fibers is not permeable through the coin, i.e., reflected from the coin. Accordingly, the coin recognition device discriminates the denomination of coins by identifying the diameter of the coins rolling through the passageway based on amount of reflected optical fibers. However, this coin recognition device has a complicated construction and is expensive due to the optical fibers.